1. Field of the Invention
The present invention relates to methods and apparatus for use with a shallow bore hole under the floor of a drilling rig in which sections of drill pipe are temporarily placed before being connected to the drill assembly, and more particularly to methods and apparatus for supporting drill pipe sections in a mouse hole adjacent to a drilling rig.
2. Description of the Prior Art
Drilling rigs are designed to drill wells deep into the earth's surface in order to extract materials such as oil, gas, etc. In order to drill effectively a great distance, the drill pipe consists of sections or “joints” of drill pipe or tubing which are continuously attached together at the drill assembly to obtain a pipe having a desired length. Such sections of drill pipe are typically 30 feet in length. In order to attach a new section of drill tubing to the existing pipe being used for the drill, the new section of drill pipe must be in a generally vertical position for attachment. Because of the weight and size of drill pipe sections, each such section of drill pipe requires support in order to be placed in a vertical orientation. In order to prepare a section of drill pipe for attachment, a common solution has been to provide a shallow bore hole adjacent to the much deeper drilling hole in the rig, into which such pipe sections are inserted in a generally vertical orientation prior to installation onto the main shaft of piping. Such shallow holes are commonly referred to as “mouse holes.”
A mouse hole is typically lined with wider piping and used as a convenient location to store the next section of drill pipe. A typical mouse-hole is usually just slightly shallower than a section of pipe. Thus, when a section of pipe is lowered into the mouse-hole, it can rest on the bottom and lean against the walls of the mouse-hole to stay in a generally vertical orientation, with the top portion of the pipe section extending above ground in order to be accessible for removal and attachment to the main drill pipe. Once the drill pipe section is placed in the mouse hole, its position is generally upright and stable, allowing the equipment used to insert pipe section to be allocated to other uses.
Generally pipe is unloaded from a truck or other delivery vehicle and placed on a pipe rack for storage. When a new section of pipe is needed, a crew brings pipe from the pipe rack using a cat line, air hoist or hydraulic winch up to the drilling floor and places it in the mouse-hole.
By placing the new drill pipe section in the mouse hole, it can be prepared for attachment to the main drill pipe while a prior section of pipe is being drilled. The prior section of pipe is drilled into the ground until it reaches a depth where it is ready for the new pipe section to be attached. While this drilling is taking place, the new pipe section is hoisted out of the mouse hole, and maneuvered near the main drill bore in a generally vertical orientation. When the prior pipe section is drilled in far enough, the vertically oriented new pipe section is attached to it, and drilling continues. Under this method, drilling must stop roughly every thirty feet (the length of a typical section of pipe) to allow for the time to add another drill pipe section.
In many cases, this process involves removing the kelley from the prior section chain of drill pipe, and moving the kelley into position over the new pipe section in the mouse-hole. The new pipe section is attached to the kelley, and raised out of the mouse-hole. The bottom of the new pipe section is attached to the end of the prior pipe section of the existing pipe chain. While drilling crews become very efficient in adding pipe sections, the process still takes considerable time, and when repeated multiple times for deep wells, this amount of non-drilling time is significant. Because of the time-consuming nature of adding drill pipe sections, it is desirable to provide methods and apparatus for more efficient and speedy attachment of drill pipe sections.
Existing mouse hole support units are generally designed to be permanently mounted into or below the floor of a drilling rig, above the mouse hole itself. They are not portable. For new installations, it is a simple matter to dig out the mouse hole itself and then install the support unit into the floor of the rig over the mouse hole as the floor and rig is constructed. However, installing such a support unit in an existing drill rig is expensive and cumbersome since it will generally involve partially demolishing or replacing the floor of the drill rig in order to provide proper support for the unit. It is therefore desirable to provide a portable mouse hole pipe support unit, and/or mouse hole pipe support units that may be installed above or on top of an existing floor of a drill rig.
Existing mouse hole support units also suffer from the drawback that they are provided in only one size, such that shims or slips are required in order for these support units to engage a given section of pipe. With these existing units, different shims or slips are required for engaging pipes having different diameters. Such mouse hole support units include a rotatable bowl surrounding an opening through which the pipe section is inserted. The circumference of the opening is designed to be larger than the largest pipe section to be used, and the circumference of the bowl is larger still. As a result, once a pipe section is inserted through the bowl and opening, it is necessary to insert a plurality of shims or slips between the pipe section and the bowl in order to hold the pipe section in place in the bowl before it can be rotated for attachment to the next pipe section.
A typical drill pipe section may nave two different diameters: a larger diameter at the ends of the section, and a narrower diameter along the middle portion of the drill pipe. The larger diameter at the end of the drill pipe creates an annular shoulder which can be used to prevent it from moving. The shims or slips are typically inserted adjacent to this annular shoulder to hold the pipe section in place when attaching one section of pipe to another, as described in U.S. Pat. No. 5,351,767. Once this attachment is achieved, the plurality of shims or slips must then be removed from the bowl so that the pipe section(s) may be removed. The insertion and removal of the shims or slips must be repeated for each pipe section that is inserted into the bowl, a process which takes considerable time. Different sizes of slips may be required for pipe section of different diameters. In addition, the slips and the frictional surfaces thereon tend to wear out from being constantly inserted and removed. It is therefore desirable to provide methods and apparatus for securely engaging pipes of different diameters in a mouse hole without the need for separate support shims or slips.